Tracing the path of a loop in a network

Abstract

A network device that can trace the path of a network loop is provided. During operation, the network device can receive a probe packet from an originating network device (OND) via an ingress port of the network device. Here, the probe packet can include a source address of the OND. The network device can determine whether the network device is the OND by comparing the source address with a local address. Upon determining that the network device is not the OND, the network device can append the local address in a payload of the probe packet and forward the probe packet via an egress port based on the destination address. On the other hand, upon determining that the network device is the OND, the network device can determine presence of a loop associated with the network device and determine a trace path of the loop based on the payload.

What is claimed is: 
     
         1 . A method comprising:
 receiving, by a network device, a probe packet from an originating network device via an ingress port of the network device, wherein the probe packet includes a source address associated with the originating network device;   determining, by the network device, whether the network device is the originating network device of the probe packet by comparing the source address with a local address of the network device;   in response to determining that the network device is not the originating network device:
 appending the local address in a payload of the probe packet; and 
 forwarding the probe packet via an egress port based on a destination address of the probe packet; and 
   in response to determining that the network device is the originating network device:
 determining presence of a loop associated with the network device; and 
 determining a trace path of the loop based on the payload of the probe packet. 
   
     
     
         2 . The method of  claim 1 , wherein, in response to determining that the network device is the originating network device, the method further comprises performing a corrective action associated with the loop, wherein the corrective action includes one or more of:
 blocking the ingress port for preventing the loop; and   generating an error notification associated with the loop.   
     
     
         3 . The method of  claim 1 , further comprising determining the probe packet as a loop detection packet based on a type of the packet. 
     
     
         4 . The method of  claim 1 , wherein, in response to determining that the network device is not the originating network device, the method further comprises appending respective identifiers of the ingress port and the egress port in the payload of the probe packet. 
     
     
         5 . The method of  claim 1 , wherein determining the trace path further comprises determining presence of a remote network device not supporting the trace path based on port information indicated in the payload of the probe packet. 
     
     
         6 . The method of  claim 1 , wherein the payload of the probe packet comprises a plurality of data sets, wherein a respective data set includes information associated with a network device included in the trace path, and wherein the information includes an address of the network device in the trace path. 
     
     
         7 . The method of  claim 6 , wherein a respective data set is represented in the probe packet based on one of:
 a type-length-value (TLV) encoded field comprising the information associated with the network device of the data set; and   a set of TLVs, each representing a piece of information associated with the network device of the data set.   
     
     
         8 . The method of  claim 1 , wherein, in response to determining that the network device is not the originating network device, the method further comprises incrementing a hop count value included in the probe packet. 
     
     
         9 . The method of  claim 8 , further comprising:
 determining whether a maximum length of the probe packet is reached; and   in response determining that the maximum length of the probe packet is reached, refraining from appending the local address in the payload of the probe packet.   
     
     
         10 . The method of  claim 1 , wherein the probe packet includes an indicator indicating support of the trace path. 
     
     
         11 . A non-transitory computer-readable storage medium storing instructions that when executed by a processor of a network device cause the network device to perform a method, the method comprising:
 receiving a probe packet from an originating network device via an ingress port of the network device, wherein the probe packet includes a source address associated with the originating network device;   determining whether the network device is the originating network device of the probe packet by comparing the source address with a local address of the network device;   in response to determining that the network device is not the originating network device:
 appending the local address in a payload of the probe packet; and 
 forwarding the probe packet via an egress port based on a destination address of the probe packet; and 
   in response to determining that the network device is the originating network device:
 determining presence of a loop associated with the network device; and 
 determining a trace path of the loop based on the payload of the probe packet. 
   
     
     
         12 . The non-transitory computer-readable storage medium of  claim 11 , wherein, in response to determining that the network device is the originating network device, the method further comprises performing a corrective action associated with the loop, wherein the corrective action includes one or more of:
 blocking the ingress port for preventing the loop; and   generating an error notification associated with the loop.   
     
     
         13 . The non-transitory computer-readable storage medium of  claim 11 , further comprising determining the probe packet as a loop detection packet based on a type of the packet. 
     
     
         14 . The non-transitory computer-readable storage medium of  claim 11 , wherein, in response to determining that the network device is not the originating network device, the method further comprises appending respective identifiers of the ingress port and the egress port in the payload of the probe packet. 
     
     
         15 . The non-transitory computer-readable storage medium of  claim 11 , wherein determining the trace path further comprises determining presence of a remote network device not supporting the trace path based on port information indicated in the payload of the probe packet. 
     
     
         16 . The non-transitory computer-readable storage medium of  claim 11 , wherein the payload of the probe packet comprises a plurality of data sets, wherein a respective data set includes information associated with a network device included in the trace path, and wherein the information includes an address of the network device in the trace path. 
     
     
         17 . The non-transitory computer-readable storage medium of  claim 16 , wherein a respective data set is represented in the probe packet based on one of:
 a type-length-value (TLV) encoded field comprising the information associated with the network device of the data set; and   a set of TLVs, each representing a piece of information associated with the network device of the data set.   
     
     
         18 . The non-transitory computer-readable storage medium of  claim 11 , wherein, in response to determining that the network device is not the originating network device, the method further comprises incrementing a hop count value included in the probe packet. 
     
     
         19 . The non-transitory computer-readable storage medium of  claim 18 , further comprising:
 determining whether a maximum length of the probe packet is reached; and   in response determining that the maximum length of the probe packet is reached, refraining from appending the local address in the payload of the probe packet.   
     
     
         20 . A computer system, comprising:
 a processor;   a set of ports;   a communication port to receive a probe packet from an originating network device via an ingress port in the set of ports, wherein the probe packet includes a source address associated with the originating network device; and   a non-transitory computer-readable storage medium storing instructions that when executed by the processor cause the computer system to:
 determine whether the computer system is the originating network device of the probe packet by comparing the source address with a local address of the computer system; 
 in response to determining that the computer system is not the originating network device:
 append the local address in a payload of the probe packet; and 
 forward the probe packet via an egress port based on a destination address of the probe packet; and 
 
 in response to determining that the computer system is the originating network device:
 determine presence of a loop associated with the computer system; and 
 determine a trace path of the loop based on the payload of the probe packet.